Looking for Meteorites with Minelab Detectors
By Vladimir Kartavzev
This experiment was inspired by the following two points:
- Minelab detectors don’t react to hot rocks. “Hot Rock” for a modern metal detector is an electromagnetic ground anomaly. The soil might be mineralized, magnetized, etc. It causes the ground to become conductive, and cause interference. Hot Rocks sometimes look like a piece of iron ore, but often look like regular rocks.
- Most metal detectors can’t be used to find rock meteorites. No one really knows what the rock meteorite looks like to the metal detector. Hence, this study was done.
Three meteorites were constructed from chondrite weighing 200, 500, and 1000 grams (0.4, 1.1, and 2.2 lbs respectively). Fine metal powder was used in the meteorites, particles smaller than 0.1 mm (0.004").
For the experiment two detectors were chosen: Explorer XS and Relic Hawk, as typical for their class (Editor’s note: both models are discontinued, however, Explorer II is very similar to Explorer XS).
The first test was an “air test”, where the detectors were placed in an empty room, without any electric wiring, metal objects, etc. Discrimination was turned off, because the meteorites contained iron eliminated by discrimination. Maximum distances at which detector recognized the object are recorded bellow in Table 1.
Table 1
Weight |
Explorer XS |
Relic Hawk |
|
8” coil |
10” coil |
15” coil |
8” coil |
15” coil |
200g (7 ounces) |
7cm (2.8”) |
10 cm (3.9”) |
10 cm (3.9”) |
7 cm (2.8”) |
10 cm (3.9”) |
500g (17.5 ounces) |
10cm (3.9”) |
10 cm (3.9”) |
10 cm (3.9”) |
10 cm (3.9”) |
10 cm (3.9”) |
1000g (35 ounces) |
10cm (3.9”) |
10 cm (3.9”) |
12 cm (4.7”) |
10 cm (3.9”) |
10 cm (3.9”) |
Analysis has led us to the conclusion that the weight of the model does not affect depth, but the concentration of metal in the model does.
To test this we had prepared several models with different iron concentration. Here are the results:
- For Explorer XS the least detectable concentration is 1.9g (0.07 ounces) or 18% of total model weight.
- For Relic Hawk the least detectable concentration is 6.2g (0.22 ounces) or 18% of total model weight.
Air test does not reflect the real conditions and detector’s abilities. Therefore a field test was conducted. A 3x3 yard square in a random field was checked by each detector to be free of any other metals. All models on the surface were picked up without a problem. The results for detection in the ground are provided in Table 2.
Table 2
|
Weight |
Explorer XS |
Relic Hawk |
|
8” coil |
10” coil |
15” coil |
8” coil |
15” coil |
1.9g (0.07 ounces) |
4cm (1.6”) |
6 cm (2.4”) |
10cm (3.9”) |
2cm (0.8”) |
6 cm (2.4”) |
6.2g (0.22 ounces) |
6cm (2.4”) |
9cm (3.5”) |
12cm (4.7”) |
4 cm (1.6”) |
11cm (4.3”) |
27g (0.95 ounces) |
15 cm (5.9”) |
19cm (7.5”) |
25 cm (9.8”) |
16cm (6.3”) |
25cm (9.8”) |
68g (2.4 ounces) |
20 cm (7.9”) |
24cm (9.4”) |
32 cm (12.6”) |
21cm (8.3”) |
36cm (14.2”) |
200g (7 ounces) |
24 cm (9.4”) |
31cm (12.2”) |
39cm (15.4”) |
26cm (10.2”) |
40cm (15.7”) |
310g (11 ounces) |
30 cm (11.8”) |
38 cm (15”) |
43cm (17”) |
33cm (13”) |
45cm (17.7”) |
Note: we had to decrease sensitivity by 30-50% in the field due to extra signals picked up due to lack of discrimination. When searching for meteorites in different ground and weather conditions the sensitivity would have to be decreased even further. This will cause a decrease in depth reading.
In a similar testing a security detector Minelab MF-1 showed an ability to detect meteorites at the depth of 8 cm (3”). While weighing only 300g (0.6 lbs) it could be used as a pinpointer.
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Translated by Dan Osipov, exclusively for Coindetector.com
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